Unidirectional fluid valve

Abstract

The exhalation valve of a respiratory face mask, while taking up only a small area, can afford extraordinarily low pressure drop for easy breathing if constructed with a valve seat having a seal edge that defines an orifice and also forms a parabola in the plane bisecting the mask. Preferably the seal edge forms a rectangle as viewed against the direction of composite fluid flow through the valve, and a flexible flap is attached to a bridge across the center of the orifice at the apex of said parabola, each end of the flap being free to be lifted to allow fluid to flow through the valve.

I claim: 
     
       1. Unidirectional fluid valve comprising: an inlet and an outlet for the flow of fluid from said inlet to said outlet;   a valve seat having a first seal edge in the form of an inflection-free concave curve, with respect to said outlet, said first seal edge including two ends, an apex intermediate said ends and a radius of curvature continually increasing from said apex to each of said ends; a second seal edge identical to said first seal edge and parallel to and spaced from said first seal edge; and two valve seat ends each connecting corresponding ends of said first and said second seal edges;   a bridge extending between said first and said second seal edges intermediate said first and said second seal edge ends, said bridge extending perpendicular to the direction of flow of said fluid from said inlet to said outlet;   a flexible flap formed of a sheet material in a generally rectangular shape and attached to said bridge and covering said valve seat in the absence of fluid flow through said valve, said flap being free to be lifted from said valve seat in response to and to accommodate fluid flow through said valve.   
     
     
       2. Unidirectional valve as defined in claim 1 wherein said valve seat ends are each straight and perpendicular to said direction of fluid flow from said inlet to said outlet. 
     
     
       3. Unidirectional valve as defined in claim 1 wherein an angle between a radius of curvature of said seal edge at one of said seal edge ends and a radius of curvature of said seal edge at said apex is greater than 15°. 
     
     
       4. Unidirectional fluid valve as defined in claim 3 wherein said angle is from 50° to 70°. 
     
     
       5. Unidirectional fluid valve as defined in claim 1 wherein said bridge is centered between said first and said second valve seal edge ends, and both ends of said flap are free to be lifted from said valve seat. 
     
     
       6. Unidirectional fluid valve as defined in claim 1 wherein said first and second valve seal edges are parabolas, and said bridge is at or near said apexes of said first and said second valve seal edges. 
     
     
       7. A respirator face mask having air-purifying means in each cheek area, between which cheek areas is mounted an exhalation valve comprising: an inlet and an outlet for the flow of fluid from said inlet to said outlet;   a valve seat having a first seal edge in the form of an inflection-free concave curve, with respect to said outlet, said first seal edge including two ends, an apex intermediate said ends and a radius of curvature continually increasing from said apex to each of said ends; a second seal edge identical to said first seal edge and parallel to and spaced from said first seal edge; and two valve seat ends each connecting corresponding ends of said first and said second seal edges;   a bridge extending between said first and said second seal edges intermediate said first and second seal edge ends, said bridge extending perpendicular to the direction of flow of said fluid from said inlet to said outlet;   a flexible flap formed of a sheet material in a generally rectangular shape and attached to said bridge and covering said valve seat in the absence of fluid flow through said valve, said flap being free to be lifted from said valve seat in response to and to accommodate fluid flow through said valve.   
     
     
       8. A respirator face mask as defined in claim 7 wherein said valve seat ends are each straight and perpendicular to said direction of fluid from said inlet to said outlet. 
     
     
       9. A respirator face mask as defined in claim 7 wherein an angle between a radius of the curvature of said seal edge at one of said seal edge ends and a radius of curvature of said seal edge at said apex is greater than 15°. 
     
     
       10. A respirator face mask as defined in claim 9 wherein said angle is from 50° to 70°. 
     
     
       11. A respirator face mask as defined in claim 7 wherein said bridge is centered between said first and said second valve seal edge ends, and both ends of said flap are free to be lifted from said valve seat. 
     
     
       12. A respirator face mask a defined in claim 7 wherein said first and said second seal edges are parabolas, and said bridge is at or near said apexes of said first and said second valve seal edges.